This invention relates, generally, to endless conveyor systems and, more particularly, to vehicle-mounted, inclinable conveyors, such as those used adjacent a stationary aircraft, and which provide a moving, continuous conveyor belt surface for receiving, transporting, and depositing a series of items such as articles of baggage or cargo.
Vehicle-mounted, inclinable conveyor belts are widely used in the aviation industry for loading and unloading aircraft. In the aviation ground support industry, such an apparatus is commonly called a belt loader. A typical belt loader has a conveyor belt which can be inclined to any position between level and a maximum height dictated by the design of the loader. The loaders are employed by placing them adjacent the fuselage of an aircraft, with the conveyor belt positioned generally perpendicular with the longitudinal axis of the fuselage, and with the elevated end of the conveyor belt placed at the bottom of an open cargo door. Depending on the conveyor belt""s direction of movement, cargo items may be either loaded into or unloaded from the aircraft. A typical belt loader is incorporated into a specialized vehicle having its own propulsion system, steering system, braking system and, of course, a seat and controls for an operator.
Several aircraft cargo belt loaders are the subjects of U.S. patents. For example, U.S. Pat. No. 4,733,767 to Anderson, et al. discloses a Low Profile Aircraft Belt Loader having a pair of electric motors to power the drive wheels and an electrically-driven hydraulic pump for actuation of a hydraulic ram, which elevates the belt conveyor. Another such loader is disclosed in U.S. Pat. No. 3,543,917 to Duerksen. The conveyor of this device incorporates a series of horizontal platforms, articulared in sections, which travel an inclined, reversible cyclic path. An early truck-mounted aircraft belt loader is disclosed is U.S. Pat. No. 3,184,045 to Fry. The truck employs a conventional automotive drive train having an internal combustion engine, a clutch and transmission mounted to the rear of the engine, and a rear-axle-mounted differential coupled to the transmission with a drive shaft. The vehicle is operated from the left side of the vehicle, as the conveyor system takes up the right side thereof.
It appears that aircraft belt loaders were adapted from other industrial equipment, such as portable mine conveyors. U.S. Pat. No. 2,428,513 discloses such a conveyor.
Most, if not all, of the currently-available aircraft belt loaders feature a drive train that is positioned along the longitudinal axis of the vehcile, much like the belt-loader of Fry, above. However, instead of being offset from the center of the vehicle, the conveyor systems are also mounted such that they are centered about the longitudinal axis of the vehicle. Such a layout makes servicing the drive train difficult, as it sits beneath the conveyor belt system. In addition, because the belt is located above the drive train, the absolute minimum height of such equipment is engine height plus the thickness of the conveyor system. However, as a practical matter, as the engine is covered, there must be additional space between the cover and the top of the engine. Currently-available belt loaders generally utilize relatively large automotive engines of 3.3 to 5.0 liter displacement (200 to 300 c.i.d.) coupled to automatic-type transmissions. Such engines have a maximum power output of between 110 and 160 horsepower.
What is needed is a vehicle-mounted aircraft belt loader which is more compact and lighter than those now available, which does not have the drive train is not mounted beneath the conveyor belt system, which has an easily controllable propulsion system for safe maneuvering around expensive aircraft, which is economical to operate both from fuel consumption and engine longevity standpoints, and which is simple to maintain and repair.
The present invention answers the heretofore expressed needs for an improved vehicle-mounted aircraft belt loader. The improved aircraft belt loader is designed such that the operator and power plant are positioned one side of the vehicle, while conveyor system is positioned on the other side thereof. Although currently produced models place the driver and power plant on the left side of the vehicle, as is U.S. convention, with the conveyor belt system on the right side, these positions may be reversed with equivalent results. The power plant, which may be an internal combustion engine, an electric motor, or a hybrid combination of internal combustion engine, generator, storage battery and electric motor, drives primary and secondary hydraulic fluid pumps. The primary pump provides pressurized hydraulic fluid used by the propulsion system. The fluid is pressurized between about 500 p.s.i. and 3200 p.s.i., that is used for the propulsion system. The secondary pump, which provides pressurized hydraulic fluid at a pressure of about 1500 p.s.i., is used to steer the vehicle, operate hydraulic pistons used to raise and lower the conveyor system, and power the conveyor belt system. By using hydrostatic drive system for vehicle propulsion, a much smaller engine is required. Small displacement engines having a maximum output of from 22 to 28 horsepower are adequate for the application. Both diesel and gasoline internal combustion engines having displacements of less than 1.67 liter (100 c.i.d.) have been used for the application. For example, a Ford VSG413 in-line, 4-cylinder, 4-stroke-cycle, 79 c.i.d. gasoline engine, which produces 28 peak horsepower at 2,800 rpm has been used with success. In fact, as there is seldom any need for more than 17 or 18 horsepower, the engine can be operated at about 1,100 rpm. Such low speed operation results in extended engine life. In addition, such low power requirements require far less fuel consumption, and the much lower output engine is much smaller and lighter that those used in the presently-available conventional belt loaders.